[pjc50]

"Lunacy" more as a modality of discussion than a property of the ideas themselves. Usually involving taking the ideas as dogma and failing to think about practical application or relevance to the particular subject under discussion.

Another example: Marx wrote a lot of reasonable analysis of the mid-19th-century economic condition (and some bad analysis). Marxists tend to be tremendously irritating write-only dogmatists. It doesn't have to be that way. The right has a similar bunch of people who are Friedman dogmatists.